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Fix: Support IPv4/IPv6 dual-stack listening on Windows (Backport from CPython) #43

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Fix: Support IPv4/IPv6 dual-stack listening on Windows (Backport from CPython) #43

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14 changes: 13 additions & 1 deletion RangeHTTPServer/__main__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,18 @@
from . import RangeRequestHandler

import argparse
import contextlib
import socket


class DualStackServer(SimpleHTTPServer.ThreadingHTTPServer):
def server_bind(self):
# suppress exception when protocol is IPv4
with contextlib.suppress(Exception):
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Copilot AI Apr 19, 2026

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contextlib.suppress(Exception) is overly broad here and can hide real bugs (e.g., programming errors or unexpected socket state). Narrow the suppression to the specific exception types expected from this setsockopt call (typically OSError / AttributeError, depending on platform) so genuine failures still surface.

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# suppress exception when protocol is IPv4
with contextlib.suppress(Exception):
# suppress expected platform/socket capability errors when protocol is IPv4
with contextlib.suppress(OSError, AttributeError):

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self.socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
return super().server_bind()
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Copilot AI Apr 19, 2026

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DualStackServer only tweaks IPV6_V6ONLY but doesn’t set address_family = socket.AF_INET6. As a result, if a user passes an IPv6 bind address like --bind ::, the underlying HTTPServer/ThreadingHTTPServer will still create an AF_INET socket and the bind will fail. To match the CPython dual-stack fix, set the server’s address_family appropriately (and ideally only use the dual-stack server when IPv6 is available via socket.has_dualstack_ipv6()).

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parser = argparse.ArgumentParser()
parser.add_argument('port', action='store',
default=8000, type=int,
Expand All @@ -28,4 +40,4 @@
help='bind to this address (default: all interfaces)')

args = parser.parse_args()
SimpleHTTPServer.test(HandlerClass=RangeRequestHandler, port=args.port, bind=args.bind)
SimpleHTTPServer.test(HandlerClass=RangeRequestHandler, ServerClass=DualStackServer, port=args.port, bind=args.bind)
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Copilot AI Apr 19, 2026

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SimpleHTTPServer.test(..., ServerClass=DualStackServer, ...) always forces the custom server class even when dual-stack IPv6 isn’t supported on the host. Consider selecting the ServerClass conditionally (e.g., use the dual-stack variant only when socket.has_dualstack_ipv6() is true and the bind address is unspecified/IPv6), and otherwise fall back to the default server class to avoid startup failures on IPv4-only environments.

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